Fluid machine

ABSTRACT

The present invention provides a fluid machine that is capable of reducing noise generated when a fluid such as compressed air passes through a discharge port and that is capable of preventing premature breakage of a discharge valve. The fluid machine comprises a cylinder head  37  that is connected to a cylinder  31 , so that the cylinder head  37 , the cylinder  31 , and a piston  32  define a compression chamber  38 . The cylinder head  37  comprises a suction port through which air is sucked into the compression chamber  38 , a suction valve for opening and closing the suction port, a discharge port  45  through which air is discharged from the compression chamber  38 , and a discharge valve  52  for opening or closing the discharge port  45 . The discharge port  45  comprises a plurality of openings  67.

BACKGROUND OF THE INVENTION

The present invention relates to a fluid machine adapted to discharge a fluid, such as air, by means of power.

A fluid machine is designed to discharge a fluid using power. As an example of a fluid machine, there can be mentioned a reciprocating-type air compressor, which comprises: a crankcase having a crankshaft rotatably disposed therein; a cylinder connected to the crankcase; a piston fitted in the cylinder so as to be capable of reciprocating therein; a connecting rod provided between the piston and the crankshaft so as to be capable of effecting a reciprocating motion of the piston according to rotation of the crankshaft; and a cylinder head which is connected to the cylinder and which, together with the cylinder and the piston, defines a compression chamber. The cylinder head is provided with a suction port through which air is sucked into the compression chamber, a suction valve for opening and closing the suction port, a discharge port through which air is discharged from the compression chamber, and a discharge valve for opening and closing the discharge port.

In such a reciprocating-type air compressor, a problem of noise is likely to occur when compressed air is discharged from the compression chamber. This noise is generated due to passage of compressed air through the discharge port. Therefore, an attempt has been made to prevent such noise by disposing an acoustic material in a discharge passage which communicates a discharge port with an air tank (see, for example, a reciprocating-type air compressor disclosed in Japanese Utility Model Application Public Disclosure No. HEI 5-12675).

Such a fluid machine as described above, which has an acoustic material disposed in a discharge passage, is effective in reducing noise when compressed air discharged from a discharge port passes through the discharge passage, and also in reducing resonant sound in an air tank. However, such a fluid machine is still unsatisfactory from the viewpoint of reducing noise generated at the instant when the compressed air is discharged through the discharge port.

The level of sound generated when compressed air passes through the discharge port can be altered by changing the size of the discharge port. For example, the level of the sound increases as the size of the discharge port increases; on the other hand, the level of the sound decreases as the size of the discharge port decreases. However, if a discharge port is made small so as to decrease the level of the sound, a flow velocity of compressed air passing thorough the discharge port becomes large. In this case, a large, concentrated shock is exerted on a discharge valve for opening and closing the discharge port. This results in premature breakage of the discharge valve.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide a fluid machine which is capable of reducing noise generated when a fluid such as compressed air passes through a discharge port and which is also capable of preventing premature breakage of a discharge valve.

To achieve the above-mentioned object, the present invention provides a fluid machine that comprises a discharge port for discharging a fluid and a discharge valve for opening and closing the discharge port, wherein the discharge port comprises a plurality of openings.

According to the present invention, the discharge port comprises a plurality of openings. Therefore, when the size of each opening of the discharge port is reduced so as to reduce noise generated when a fluid such as compressed air passes through the discharge port, the fluid can be passed through each opening at a relatively low flow velocity. Therefore, a shock of the fluid against the discharge valve for opening and closing the discharge port can be reduced. Further, by dividing the discharge port into a plurality of openings, the shock of a fluid such as compressed air against the discharge valve can be dispersed. Therefore, it is possible to reduce noise generated when a fluid such as compressed air passes through the discharge port while preventing premature breakage of the discharge valve.

In the above-mentioned fluid machine of the present invention, the discharge port may comprise three or more openings.

When the discharge port comprises three or more openings, for example, in a case that the discharge valve has a circular sealing surface, a well-balanced disposition of the openings in terms of surface area relative to the sealing surface can be achieved. Therefore, even when a fluid such as compressed air that has passed through the openings exerts a shock on the discharge valve, the discharge valve can evenly receive the shock. Therefore, the discharge valve has a longer lifetime than it would if it received the shock unevenly.

Further, in the present invention, the discharge valve may have a circular sealing surface, with the three or more openings being evenly arranged with respect to the center of the sealing surface as a center.

When the discharge valve has a circular sealing surface, with the three or more openings being evenly arranged with respect to the center of the sealing surface as a center, a well-balanced disposition of the openings in terms of surface area relative to the circular sealing surface can be obtained. Therefore, even when a fluid such as compressed air that has passed through the openings exerts a shock on the discharge valve, the discharge valve can evenly receive the shock. As a result, the discharge valve has a longer lifetime than it would if it received the shock unevenly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section view of a fluid machine according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of an essential part of the fluid machine according to the embodiment of the present invention.

FIG. 3 is a plan view of a discharge port of the fluid machine according to the embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinbelow, referring to the accompanying drawings, description is made in detail with regard to a fluid machine according to an embodiment of the present invention.

A fluid machine 20 in this embodiment is used to supply compressed air to an air suspension of an air suspension system mounted on a vehicle such as an automobile. In a lower part of the fluid machine 20, a crankcase 22 is connected to a motor case 21. A motor 24 is accommodated in the motor case 21 in a manner such that an output shaft 23 of the motor 24 protrudes into the crankcase 22.

The output shaft 23 of the motor 24 is rotatably supported at its intermediate portion by the crankcase 22 via a bearing 26 and is fixed, at its forward end portion protruding into the crankcase 22, to a crank member 27, which extends in a direction perpendicular to the output shaft 23. Further, a crankpin 28 is supported, by the crank member 27, in a direction parallel to the output shaft 23 of the motor 24. With this arrangement, the crankpin 28 is adapted to perform an orbiting motion about the output shaft 23 via the crank member 27, according to rotation of the output shaft 23 of the motor 24. As a result, the output shaft 23, the crank member 27, and the crankpin 28 constitute a crankshaft 29, which is rotatably disposed in the crankcase 22.

A cylinder 31 is mounted on and connected to an upper portion of the crankcase 22. A piston 32 is fitted into the cylinder 31 so as to be capable of reciprocating therein. A connecting rod 34 is pivotally connected at one end thereof to the piston 32 via a piston pin 33. The other end of the connecting rod 34 is pivotally connected via a bearing 35 to the crankpin 28 of the crankshaft 29. Therefore, when the crankpin 28 performs an orbiting motion according to operation of the motor 24, the piston 32 reciprocates in the cylinder 31 via the connecting rod 34. In other words, the connecting rod 34 disposed between the piston 32 and the crankshaft 29 effects a reciprocating motion of the piston 32 according to rotation of the crankshaft 29.

A cylinder head 37 is mounted on and connected to the upper portion of the cylinder 31. The cylinder head 37, together with the cylinder 31 and the piston 32, defines a compression chamber 38. In the cylinder head 37 are formed a suction passage 42 and a discharge passage 46. The suction passage 42 has an external air inlet 40, on one end, which is exposed to the outside of the machine, and a suction port 41, on the other end, which is open to the compression chamber 38 and through which air is sucked into the compression chamber 38. The discharge passage 46 has a connection port 44, on one end, which is connected to an air drier 43 for dehumidifying air and a discharge port 45, on the other end, which is open to the compression chamber 38 and through which air is discharged from the compression chamber 38.

The suction passage 42 is provided with a suction valve 48 for opening and closing the suction port 41. The suction valve 48 opens and closes so as to allow only a flow of air from the external air inlet 40 to the suction port 41. The suction valve 48 comprises a valve body 49 for opening and closing the suction port 41, and a spring 50 which urges the valve body 49 in a direction for closing the suction port 41. When a pressure in the compression chamber 38 becomes lower than an external air pressure by more than an urging force of the spring 50, the valve body 49 moves so as to open the suction port 41.

The discharge passage 46 is provided with a discharge valve 52 for opening and closing the discharge port 45. The discharge valve 52 opens and closes so as to allow only a flow of air from the discharge port 45 to the connection port 44. The discharge valve 52 comprises a poppet-type valve body 53 which is made of a synthetic resin and is adapted to open or close the discharge port 45, and a spring 54 which urges the valve body 53 in a direction for closing the discharge port 45. When a pressure in the compression chamber 38 becomes larger than a pressure in the connection port 44 by more than an urging force of the spring 54, the valve body 53 moves so as to open the discharge port 45.

The air dryer 43 comprises a dryer case 58 which has an air passage opening 56 connected to the connection port 44 and an air passage opening 57 communicating with a place to which the compressed air is to be supplied. An air-permeable partition plate 60 and an air-permeable partition plate 61 are fittingly disposed on the air passage opening 56 side and on the air passage opening 57 side, respectively, inside the dryer case 58. A large number of spherical silica gel particles (moisture adsorbent) 63 are filled in an adsorption chamber 62 defined by the partition plates 60 and 61. Further, a spring 64 is interposed between the partition plate 61 and the dryer case 58 so as to press the partition plate 61 toward the partition plate 60. As a result of pressing the partition plate 61, the silica gel particles 63 are filled at high density in the adsorption chamber 62 between the partition plates 60 and 61.

In this embodiment, as shown in FIGS. 2 and 3, the discharge port 45 of the discharge passage 46 comprises a plurality of openings 67; specifically, seven openings 67, of the same diameter. These openings 67 are opened or closed all at once by the valve body 53. The valve body 53 has a flat, circular sealing surface 70. The sealing surface 70 is adapted to abut against a flat valve seat surface 68, at which the openings 67 are open on a side opposite from the compression chamber 38, to thereby close the openings 67. The plurality of openings 67 are formed in a manner such that when the sealing surface 70 abuts against the valve seat surface 68, the plurality of openings 67 are evenly arranged within the sealing surface 70 in a circumferential direction thereof.

Illustratively stated, one of the openings 67 is located at a central portion of the sealing surface 70, and the other six openings 67 are located at the same radial distance from the center of the sealing surface 70 and at every 60 degrees so as to be equally spaced in the circumferential direction of the sealing surface 70. In this manner, the seven openings 67 are evenly arranged with respect to the center of the sealing surface 70 as a center. Therefore, relative to the sealing surface 70, there is no imbalance in terms of surface area between a portion at which the openings 67 are formed and a portion at which no openings 67 are formed. To achieve such a well-balanced disposition relative to the sealing surface 70 without imbalance in terms of surface area between a portion at which the openings 67 are formed and a portion at which no openings 67 are formed, it is preferable to form three or more openings 67. When the openings 67 have the same diameter, it is preferable to space the openings 67 equally in the circumferential direction.

In arranging a plurality of openings, the openings do not have any restrictions on the size (the area of the opening), shape, and so on, as long as a resultant force of forces which are applied to the valve body 53 by compressed air discharged from the plurality of openings acts on the center of the valve body 53 in a direction for opening the valve body 53 (an upward direction in FIG. 2).

The force applied to the valve body 53 by compressed air discharged from each of the openings can be estimated by calculating a pressure loss, based on the size, the shape and the length (in a direction of flow of compressed air) of the opening. Alternatively, it can be determined directly by discharging compressed air from one of the openings while sealing the other openings.

The above-mentioned resultant force can be determined by composition of the above-mentioned forces generated in all of the respective openings, using a method similar to a method of calculating a center of mass in a mass system. Specifically, the resultant force can be determined in the following way.

When the magnitude of a force applied to the valve body 53 by compressed air discharged through each opening is indicated by F_(i) and the coordinates of a point on an area of discharge are indicated by X_(i) and Y_(i), coordinates X and Y of the resultant force can be represented by the following equations: X=(ΣF _(i) X _(i))/(ΣF _(i)) Y=(ΣF _(i) Y _(i))/(ΣF _(i))

Further, the magnitude of the resultant force can be calculated by summing the forces generated in all the respective openings.

When the motor 24 of the fluid machine 20 with the structure described above is actuated, the output shaft 23 of the motor 24 starts to rotate, which makes the crankpin 28 perform an orbiting motion via the crank member 27. According to this orbiting motion of the crankpin 28, the piston 32 performs a reciprocating motion in the cylinder 31 via the connecting rod 34, thus increasing and decreasing a volume of the compression chamber 38. When the volume of the compression chamber 38 is increased, the suction valve 48 opens, to thereby introduce external air into the compression chamber 38 through the suction passage 42. When the volume of the compression chamber 38 is decreased, the air in the compression chamber 38 is compressed and the discharge valve 52 opens due to the effect of pressure of the compressed air. When the discharge valve 52 opens, the compressed air is discharged through the plurality of openings 67 of the discharge port 45 and the discharge passage 46.

Each of the openings 67 is made small in diameter; therefore, noise generated when the compressed air passes through the openings 67 can be reduced, to thereby exert an excellent silencing effect. Further, although the size of each opening 67 is small, due to formation of the plurality of openings 67, a flow velocity of the compressed air passing through each opening 67 can be reduced. As a result, a shock of the compressed air against the valve body 53 of the discharge valve 52 for opening and closing the openings 67, which is made of a synthetic resin, can be reduced. Further, by dividing the discharge port 45 into the plurality of openings 67, the shock of the compressed air against the valve body 53 can be dispersed. Therefore, premature breakage of the valve body 49 of the discharge valve 52 can be prevented while reducing noise generated when the compressed air passes through the discharge port 45.

The discharged compressed air as described above is introduced through the air passage opening 56 into the dryer case 58 of the air dryer 43 and is passed through the partition plate 60 and then through the adsorption chamber 62, where the compressed air is dehumidified by the silica gel particles 63 which adsorb moisture of the compressed air. Thereafter, the compressed air passes through the partition plate 61 and is discharged through the air passage opening 57.

In this embodiment, the discharge port 45 is divided into the three or more openings 67, and the discharge valve 52 has the circular sealing surface 70. With this arrangement, as described above, a well-balanced disposition of the openings 67 in terms of surface area relative to the sealing surface 70 can be achieved. Therefore, even if compressed air through the openings 67 exerts a shock on the discharge valve 52, the discharge valve 52 evenly receives the shock, so that the discharge valve has a longer lifetime than it would if it received a shock unevenly.

The plurality of openings 67 of the discharge port 45 may be formed in a separate sintered component during sintering, which component is attached to a hole for attachment formed in the cylinder head 37. In this way, formation of the plurality of openings 67 can be readily conducted.

This embodiment has exemplified compressed air as a fluid. However, the fluid can be any other gas, a liquid such as water or oil, or any other fluid. Further, the fluid machine used in this embodiment is a so-called reciprocating-type air compressor; however, it can be a scroll-type or rotary-type fluid machine or the like, as long as it is provided with a discharge port and a discharge valve.

Although only one exemplary embodiment of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teaching and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.

The entire disclosure of Japanese Patent Application No. 2004-286901 filed on Sep. 30, 2004 including specification, claims, drawings, and summary is incorporated herein by reference in its entirety. 

1. A fluid machine comprising a discharge port for discharging a fluid and a discharge valve for opening and closing the discharge port, wherein the discharge port comprises a plurality of openings.
 2. A fluid machine according to claim 1, wherein the discharge port comprises three or more openings.
 3. A fluid machine according to claim 2, wherein the discharge valve has a circular sealing surface and the three or more openings are evenly arranged with respect to the center of the sealing surface as a center.
 4. A fluid machine according to claim 3, wherein the three or more openings have the same diameter and are spaced equally in a circumferential direction of the sealing surface.
 5. A fluid machine according to claim 4, wherein the discharge valve is a poppet valve made of a synthetic resin.
 6. A fluid machine according to claim 1, wherein the fluid machine is an air compressor.
 7. A fluid machine according to claim 2, wherein the fluid machine is an air compressor.
 8. A fluid machine according to claim 3, wherein the fluid machine is an air compressor.
 9. A fluid machine according to claim 4, wherein the fluid machine is an air compressor.
 10. A fluid machine according to claim 5, wherein the fluid machine is an air compressor.
 11. A fluid machine according to claim 1, wherein the discharge valve comprises a valve body and wherein a resultant force of forces which are applied to the valve body by compressed air discharged through the plurality of openings acts on the center of the valve body in a direction for opening the valve body. 